Unsaturated organoalkoxysilanes containing an acryloyloxy group, such as 3-acryloyloxypropyltriethoxysilane, have been produced by the nucleophilic substitution reaction of a haloorganoalkoxysilane with a metal salt of an unsaturated carboxylic acid, such as sodium acrylate, in the presence of a suitable phase-transfer catalyst. In addition to the desired silane product, this process produces a crude mixture comprising the acryloyloxysilane, a metal halide precipitate, and unreacted reactants. The metal halide precipitate is removed by filtration or washing with brine or water.
Although there are methods of removing the unreacted starting materials, solvents, and unwanted reaction products, these methods have not been adequate to produce acryloyloxysilanes with the low levels of impurities, such as unreacted starting materials, demanded by many of the applications where acryloyloxysilanes are used today. One of the issues with the present methods is that the starting material and the acryloyloxysilanes may vaporize at similar temperatures making separation by distillation difficult. Furthermore, repeated distillation steps required to separate the starting materials sometimes cause the formation of dimers and other oligomers of the target acryloyloxysilane product reducing yields and further increasing impurity issues.
Therefore, there is a need for processes for purifying acryloyloxysilanes that quickly separate unreacted starting materials, solvents, and undesired reaction products from the desired acryloyloxysilane without reducing yields through the formation of dimers and other oligomers of the acryloyloxysilane.